who has custom intake plem??

[Derby]

I believe I begin to understand you.

A intake as I think it should be made. (better is a variable intake but that quite hard to draw)





The runners are blue. The runners should be the same length. The turn must be gentle. The begin of the runner should be rounded to avoid turbulence.
The plenum (bubblegum)should be about ten times the displacement. But that is quite hard to make under todays hood.
The green pipe is for connection with air filter/intercooler/turbo

It looks like the NA gts intake but without the 90 turns.

Derby

[RazorGTR]

I'll do one up in Solid works and take some screen shots.

What software do you use by chance?

[my3rdskyline]

I didn't read too deeply into the thread so forgive me but I thought this was a pretty cool idea for non RB26's:

http://www.cardomain.com/memberpage/492821/2

[RazorGTR]

Very simular to some of the other custom built one's I've seen. Not a too bad of a job but looks like they went a bit overkill on the welding.

[Derby]

Originally Posted by my3rdskyline

I didn't read too deeply into the thread so forgive me but I thought this was a pretty cool idea for non RB26's:

That intake is a nice try but the runners are to short. And the plenum is to small. It cannot hold much air.

don't get me wrong it is a good intake. but it looks like it was some 10-minute-intake.

(But i have to admit there isn't much space for something better)

@RazorGTR Love to see your picture/drawing/design
It took me 3 hours to draw this. And the bents in the runners was new to me.

I use Autodesk Inventor 8. Very, very userfriendly

Derby

[SkylineUSA]

Shorter the runners the better

[Derby]

WRONG. (no offence)

The longer the runners the better(which isn't true for all applications). The runners on the pic of the nissan 2500. are way to short for the rpm range the engine can reach. those runners are usefull for F1 engines (reach 19000 rpm)

With longer runners u can use natural physics to fill your cil.

Has to do with pressure waves. But you already know that.

Derby

[SkylineUSA]

Originally Posted by Derby

WRONG. (no offence)

The longer the runners the better(which isn't true for all applications). The runners on the pic of the nissan 2500. are way to short for the rpm range the engine can reach. those runners are usefull for F1 engines (reach 19000 rpm)

With longer runners u can use natural physics to fill your cil.

Has to do with pressure waves. But you already know that.

Derby

Derby,

Shorter the better, but yes they can be too short. Just trying to get a rise out of you I'll get into this disscusion when I have more time. Its been pretty good so far, and everything has been well written. Good to see some tech stuff in here. Big thumbs up

[RazorGTR]

While in some cases longer runners are better, in turbo or supercharged cars where the intake system is pressurized it isn't as critical. Actually the more turbulance you create in a natrually asperated application the better. This helps atomize the fuel better.
In injected cars, let me rephrase that, port injected cars air turbulance is a bad thing. The injector amtomized the fuel or is suppose to. It injects a fine mist instead of dropplets like in TBI or carburated.

On a plenum the idea is in a round-about way, to store air under pressure so when the intake valve opens there is sufficent air mass to fill the cylinder. Now in a high reving engine or one that has a large capacity this becomes more relivent.

Space is also a consideration, and along with flow and design. There are many theories and calculations on this. A smother transition will always fill a given volume better than one that is filled with turbulance when under pressure. At vaccum though this is changed. It is hard to explain but when tested with smoke filled air into a glass jar you would see what i mean.

[Derby]

@SkylineUSA:

I really like this discussion as well, So keep up the good work.

@RazorgtR:

I as fas as i know the bigger the plenum the better. The bigger the plenum the better turbulence is turned into quite air (colisions (crashes) with other aotoms/moleculs). Also for the engine it looks like it is sucking air from a room where the pressure is pressure at sealevel. It can suck air without any obstruction( airfilter, badly designed box to plenum pipes)Therefor the plenum must contain air for more then one cilinder to keep the pressure the same as the surroudings. Like a Common rail diesel.

Runners.
by opening the the inlet valve a pressure wave (negative -) is travelling into the cilinder. by closing the cilinder a pressure wave (positive +) is bouncing upon the valve. This +wave is going back to the plenum where it returns as a -wave back to the valve. It bounces back on the closed valve and it travels back to the plenum still as a -wave. By entering the plenum the sign (-/+) switches (here from - to +) and begins he travel to the inlet valve as a positive wave.
Now the engineer who works on the intake has to get the +wave at the inlet valve as it is 1 mm open.
In case of my car I have to get 9 meters (29.52747 feet)of runner (one runner 4 in total) under the hood to get more torque on the by my desired(there is something wrong on this word) rpm (2500).
The pulses (positive/negative wave) travel at 343 meter/s (0.2131303 mile per second) at 25C (77 Fahrenheit) and every 20 C that the air is hotter the speed raises 11m/s so lets take an air temperature of 65 C the speed of sound is 365 m/s at this temp. (0.2268005 mile per second). 7000 rpm is 116 rps. Every 720 degrees a combustion. So every 720 degrees the intake valve opens once. So from those 116 rps the inlet opens 58 times (please people correct me if I'm wrong. It is late for me). I pick a cam that is used for an NA Renault Alpine (I got the data on my desktop... everybody is lazy sometimes ). Every work process takes 1/116 seconds (0.008620). From every work process the inlet is 255 degress open. so the inlet is closed for 720-255 = 465 degrees. That is 0.005567 seconds. So a +wave(back) a -wave (to) a -wave (back) and a +wave(to the valve) has to travel in 0.005567 second. The speed of sound is 365 meter per second, so the inlet has to be 365*0.005567 = 2 meters (6.56166 feet)(that is a lot...) long to have advantage of the pressure waves in the inlet. This advantage is used for this rpm but it also works when the inlet is already open. (not when closed of course) So it works for something more then one rpm. This creates a mountain landscape in a graph.
(This is all just an example, I took the time for this but it still can contain mistakes)
It also works on the 3500 rpm. but the pressure waves have to travel 4 times (up and down). But the effect is less cause of efficiency.
This is all for NA engines. I still don't know how it works for turboed engines. I think it works the same because of the natural effect. But if someone thinks different please let it know.

No offence SkylineUSA but shorter runners work only for high reving motors. Like F1. The best would be a engine without any kind of runners...

I hope this clears something up. This however is not the only way to desing runner length. There are two other ways to come to a runner length. The art is to combine all of them.
Most of todays intakes are designed around the exhaust. The exhaust works on a similar way. But there are also some other things that work on a exhausts. Cause of the change between negative effect and positive, the intake is designed to compensate for the negative effects of the exhaust.

Derby

[RazorGTR]

Just so you guys know I stuck the thread because it is one of the BEST on intake systems bar none.

Darby that is well and truely over my head. While i understand the basic principles and theories you've reached a new platto, good on ya!

From what I've been able to dig up on the top hp cars using forced induction, ie turbo in this case, the shorter the runners and size/shape of the expansion chamber does make a difference. While what i can explain is turbulance, but not the indepth you have. It seems from what I've been able to find a larger frontal area of the plenum and sloping down to a smaller rear section is what seems to be the go for these application. The area I do agree must be able to support much more than what the individual cylinder capacity is. This is without a doubt common sense in the intake world. While I'm not designer for intakes, I go by what I see the top cars using.

To be able to squeeze 1,400+hp out of a 2.6 - 2.8 litre motor they all seem to use the same basic shape plenum. Keep in mind all these cars are using extremely large front mounted intercoolers there for the intake charge temp is greatly reduced. What you don't want is the air inside the intake system to be there long enough to then again re-heat up. This in fact would negate cooling the intercooler is doing and you get no gains.

In keeping with the high rpms for a mass produced turbo motor to rev to 8,200rpms factory you then can see why the shape, size, and runner lengths are what they are. HKS, VEILSIDE, JUN, TOP SECRET, etc all use plenums of nearly identical shapes and configurations. All have cars making extreme amounts of power using gas (race gas but still gas).

Most high performance plenums I've seen for the RB series motors are extremely thin. They would be in the area of 1.5mm - 2mm thick. Why I have not idea other than weight savings.

Something else has been sitting with me. You've memtioned the "shockwave" effect of the valves opening an closing, while that would be an issue with an N/A engine, when you have the intake system under constant pressure this would be reduced. Air compresses only a given amount, and even at that the amount the valves would move I honestly can't see it making that much of an impact on a forced induction small capicity engine. The larger N/A motors with very large lifting valves, which are also much larger would make a lot more sense.

[Derby]

@ RazorGTR:
Thanx for the the compliments.

What I calculated was mentioned for a NA car. NA cars have serious trouble to get enough air into the cilinder. And most of the NA cars don't have an intercooler. So warming up agian is ot much of an issue. For turbo cars with large coolers it is better to have a small plenum. That is something i never thought about really.

I'm gonna comment on this later on the day. Have to work a little more, while i'm think of what you said. Could you post a pic of an HKS intake (or veilside or jun doesn't matter really)?

Derby

[Derby]

@RazorGTR (and the other that follow this)

The intake you describe (big plenum at beginning and smaller at the end)must be the best there is cause it is used on many engines. Plenum size is the big questionmark. I looked for some relations ships between power, cilinder fill rate and plenum size but there is none (as far as i have seen). Some people talk about ten times the displacement, other only two times.

looking at what other designed thought is almost the best way to learn. (asking and discussion the design is one little step better, but it is hard to find the people who really know stuff)

What i forgot to tell about runners is that they have to be (i think you call it tapped) bigger at the entrance and smaller at the cilinder head. This depens on the material used and the turbulence it is creating close to the side of the runner.

About the speed of sound in pressurized enviroment. The speed slows down at greater pressures. So for a turbo engine the runners can be shorter to have advantage of the pressure waves. Found on the net (learing new things all day is fantastic... )
In mediums with very high densities indiviual particles have greater inertia and they are less responsive to the interactions between neighboring particles. So at greater densities sound waves will move slower, if all other factors are equal. Thus, a sound wave will travel nearly three tmies faster in Helium gas as it will in air; this is due to the lower mass of Helium particles as compared to air particles.

about the time the wave is working in pressure. I can't find any relation to a life time of a wave in pressure. I know that a pressure wave is dampered when travelling through the runner. ( advantage of waves works for 16 sign (-/+) chances) i wanto believe the wave is canceled earlier but i can't find any proof of it.

The wave is made by closing the valve. The force the wave has is determent by the speed the valve closes. Force is slightly influenced by the size of the valve. (a big valve houses in a big runner in the head. if the big valve is placed at the end of a small area runner the force will by greater by cause of turbulence the effect will soon be away.) So a steepper cam has more influence on the 'lifetime' of the wave.

Derby

[firefighter0143]

i read on a issue of turbo magizine.....a toyota supra gaining around 72 bhp
on a vielside plenum......geez thats a lot or hp gian..
but then agian thats with a larger trottle body too

[Derby]

it is quite hard to compare these things. Maybe was the x brand intake very very bad. And what is the gain in percentages?
It is all relative

Derby